1. Field of the Invention
This invention relates to a printing control system for a printer such as a stencil printer in which two or more printing papers can be simultaneously present on its printing path.
2. Description of the Related Art
In a printer such as a stencil printer, the printing action of the printer including supply of printing papers from a paper supply table to a printing mechanism, transfer of ink through a stencil on a printing drum in the printing mechanism and discharging printed papers from the printing drum to a paper discharge table is controlled by a printing control system provided in the printer. The printing control system executes mainly the steps of starting the paper feed mechanism, checking whether paper supply has been successfully performed, pressing the printing paper against the printing drum, checking whether paper discharge has been successfully performed, updating the total count of the numbers of prints and the like and controls these steps in sequence according to the status of sensors and/or the angular position of the printing drum.
In a single-drum stencil printer (a stencil printer having a single printing drum), one printing paper is fed to the printing drum each time the printing drum makes one rotation. Since the printing drum makes two rotations from the time each printing paper is fed from the paper supply table to the time the printing paper is discharged to the paper discharge table, two papers are simultaneously present on the printing path of the single-drum stencil printer in the steady state of printing, that is, except when a first printing paper is fed and when a last printing paper is fed. The xe2x80x9cprinting path of the printerxe2x80x9d is a path along which the printing papers are fed from the paper supply table to the paper discharge table. In the case of a single-drum stencil printer, the xe2x80x9cprinting pathxe2x80x9d is a path between the paper feed table and the paper discharge table including the paper feed mechanism, the pressing mechanism, the printing drum, the paper discharge mechanism and the like.
In printers having two or more printing drums, more printing papers are simultaneously present on the printing path.
The printing control system must detect the paper jam for all the printing papers present on the printing path. From the viewpoint of the flow of the printing steps, the step of starting the paper feed mechanism for feeding the following printing paper and the step of checking whether supply of the following printing paper has been successfully performed should be done before the step of checking whether the preceding printing paper has been successfully discharged. Only this requisition complicates the processing by the printing control system. Requisition involved by the fact that since only one printing paper is present on the printing path in the period when a first printing paper is fed from the paper feed table and the period when a last printing paper is discharged to the paper discharge table, control processing different from that for the steady state of printing must be incorporated in order to deal with the periods and the fact that special situations, e.g., a situation where void feed (no printing paper is fed) is made, a situation where printing is to be made on longer printing papers, and the like, must be dealt with, further complicates the processing by the printing control system in order to realize proper paper jam detection.
In view of the foregoing observations and description, the primary object of the present invention is to provide a printing control system which can make the printing control easily and precisely in a printer where two or more printing papers can be simultaneously present on its printing path.
In accordance with the present invention, there is provided a printing control system for a printer comprising the same number of one-page control means as the number of printing papers which can be simultaneously present on the printing path of the printer at the maximum and a main control means which starts one of the one-page control means which are free each time a printing paper is supplied, wherein each of said one-page control means controls printing action on the corresponding printing paper from the step of supplying the corresponding printing paper to the step of discharging the corresponding printing paper and is made free when the printing action on the corresponding printing paper is successfully finished or when an error is detected during the printing action on the corresponding printing paper.
That is, in the printing control system of the present invention, unlike the convention printing control system where printing actions on all the printing papers present on the printing path are controlled in sequence by the printing control system, the printing action on each of the printing papers is controlled by one one-page control means and each one-page control means is started by the main control means each time one printing paper is supplied. Accordingly, control of the printing action is facilitated and accuracy in paper jam detection can be improved.
When said printing action is stencil printing, the one-page control means executes the steps of starting the paper feed mechanism, checking whether paper supply has been successfully performed, pressing the printing paper against the printing drum, checking whether paper discharge has been successfully performed, and the like.
It is preferred that the one-page control means provides a warning when it detects an error during the printing action on the corresponding printing paper.
The one-page control means may provide a warning, for instance, by displaying a message xe2x80x9cpaper jamxe2x80x9d on a screen of a control panel of the printer or by outputting an error detection signal to the main control means to cause the main control means to display an error massage on a screen or to interrupt the printing.
In the printing control system of the present invention, since control of the printing action is distributed among the one-page control means and the main control means so that the main control means only has to check the timing of paper supply and check the signal from each one-page control means while each of the one-page control means only has to control printing action on a single printing paper, control of the printing action is facilitated in total and a situation where void feed is made, and a situation where printing is to be made on longer printing papers can be easily dealt with.
When the one-page control means is arranged to provide a warning when it detects an error during the printing action on the corresponding printing paper, the operator can be informed of an error earlier and can deal with the error more rapidly.